We don’t know what causes each case of laryngeal or hypopharyngeal cancer. But we do know many of the risk factors for these cancers (see "What are the risk factors for laryngeal and hypopharyngeal cancers?") and how some of them cause cells to become cancerous.
Scientists believe that some risk factors, such as tobacco or heavy alcohol use, may cause these cancers by damaging the DNA of cells that line the inside of the larynx and hypopharynx.
DNA is the chemical in each of our cells that makes up our genes — the instructions for how our cells function. We usually look like our parents because they are the source of our DNA. However, DNA affects more than how we look. Some genes have instructions for controlling when cells grow and divide. Genes that promote cell division are called oncogenes. Genes that slow down cell division or cause cells to die at the right time are called tumor suppressor genes. Cancers can be caused by DNA changes that turn on oncogenes or turn off tumor suppressor genes.
Some people inherit DNA mutations (changes) from their parents that greatly increase their risk for developing certain cancers. But inherited oncogene or tumor suppressor gene mutations are not believed to cause very many cancers of the larynx or hypopharynx.
Gene changes related to these cancers usually start during life rather than before birth like an inherited mutation does. These acquired mutations often result from exposure to cancer-causing chemicals, like those found in tobacco smoke. Acquired changes in genes, such as the p53 and p16 tumor suppressor genes, seem to be important in the development of larynx and hypopharynx cancers, although not all cancers have these changes. Several different gene changes are probably needed for cancer to develop, and not all of these changes are understood at this time.
Inherited mutations of oncogenes or tumor suppressor genes rarely cause these cancers, but some people seem to inherit a reduced ability to detoxify (break down) certain types of cancer-causing chemicals. Others may inherit an increased tendency to activate cancer-causing chemicals, making them even more dangerous. These people are more sensitive to the cancer-causing effects of tobacco smoke, alcohol, and certain industrial chemicals. Researchers are developing tests that may help identify such people, but these tests are not yet reliable enough for routine use. Therefore, doctors recommend that all people avoid tobacco smoke and hazardous industrial chemicals.
Some forms of human papilloma virus (HPV) are emerging as important causes of some throat cancers (including cancers of the hypopharynx). Patients who develop HPV-associated hypopharyngeal cancers are less likely to have exposure to tobacco and alcohol. The outlook of HPV-associated head and neck cancers appears to be better than for HPV-negative head and neck cancers.
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